A new 3-D modelling method to extract subtransect dimensions from underwater videos

Underwater video transects have become a common tool for quantitative analysis of the seafloor. However a major difficulty remains in the accurate determination of the area surveyed as underwater navigation can be unreliable and image scaling does not always compensate for distortions due to perspec...

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Main Authors: L. Fillinger, T. Funke
Format: Article
Language:English
Published: Copernicus Publications 2013-04-01
Series:Ocean Science
Online Access:http://www.ocean-sci.net/9/461/2013/os-9-461-2013.pdf
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spelling doaj-96a30cc00cc4476cb0c59ab8d6b3abd22020-11-25T01:46:20ZengCopernicus PublicationsOcean Science1812-07841812-07922013-04-019246147610.5194/os-9-461-2013A new 3-D modelling method to extract subtransect dimensions from underwater videosL. FillingerT. FunkeUnderwater video transects have become a common tool for quantitative analysis of the seafloor. However a major difficulty remains in the accurate determination of the area surveyed as underwater navigation can be unreliable and image scaling does not always compensate for distortions due to perspective and topography. Depending on the camera set-up and available instruments, different methods of surface measurement are applied, which make it difficult to compare data obtained by different vehicles. 3-D modelling of the seafloor based on 2-D video data and a reference scale can be used to compute subtransect dimensions. Focussing on the length of the subtransect, the data obtained from 3-D models created with the software PhotoModeler Scanner are compared with those determined from underwater acoustic positioning (ultra short baseline, USBL) and bottom tracking (Doppler velocity log, DVL). 3-D model building and scaling was successfully conducted on all three tested set-ups and the distortion of the reference scales due to substrate roughness was identified as the main source of imprecision. Acoustic positioning was generally inaccurate and bottom tracking unreliable on rough terrain. Subtransect lengths assessed with PhotoModeler were on average 20% longer than those derived from acoustic positioning due to the higher spatial resolution and the inclusion of slope. On a high relief wall bottom tracking and 3-D modelling yielded similar results. At present, 3-D modelling is the most powerful, albeit the most time-consuming, method for accurate determination of video subtransect dimensions.http://www.ocean-sci.net/9/461/2013/os-9-461-2013.pdf
collection DOAJ
language English
format Article
sources DOAJ
author L. Fillinger
T. Funke
spellingShingle L. Fillinger
T. Funke
A new 3-D modelling method to extract subtransect dimensions from underwater videos
Ocean Science
author_facet L. Fillinger
T. Funke
author_sort L. Fillinger
title A new 3-D modelling method to extract subtransect dimensions from underwater videos
title_short A new 3-D modelling method to extract subtransect dimensions from underwater videos
title_full A new 3-D modelling method to extract subtransect dimensions from underwater videos
title_fullStr A new 3-D modelling method to extract subtransect dimensions from underwater videos
title_full_unstemmed A new 3-D modelling method to extract subtransect dimensions from underwater videos
title_sort new 3-d modelling method to extract subtransect dimensions from underwater videos
publisher Copernicus Publications
series Ocean Science
issn 1812-0784
1812-0792
publishDate 2013-04-01
description Underwater video transects have become a common tool for quantitative analysis of the seafloor. However a major difficulty remains in the accurate determination of the area surveyed as underwater navigation can be unreliable and image scaling does not always compensate for distortions due to perspective and topography. Depending on the camera set-up and available instruments, different methods of surface measurement are applied, which make it difficult to compare data obtained by different vehicles. 3-D modelling of the seafloor based on 2-D video data and a reference scale can be used to compute subtransect dimensions. Focussing on the length of the subtransect, the data obtained from 3-D models created with the software PhotoModeler Scanner are compared with those determined from underwater acoustic positioning (ultra short baseline, USBL) and bottom tracking (Doppler velocity log, DVL). 3-D model building and scaling was successfully conducted on all three tested set-ups and the distortion of the reference scales due to substrate roughness was identified as the main source of imprecision. Acoustic positioning was generally inaccurate and bottom tracking unreliable on rough terrain. Subtransect lengths assessed with PhotoModeler were on average 20% longer than those derived from acoustic positioning due to the higher spatial resolution and the inclusion of slope. On a high relief wall bottom tracking and 3-D modelling yielded similar results. At present, 3-D modelling is the most powerful, albeit the most time-consuming, method for accurate determination of video subtransect dimensions.
url http://www.ocean-sci.net/9/461/2013/os-9-461-2013.pdf
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